Therapeutic oligonucleotides, in particular, micro RNA (miR), hold great promise to become effective anticancer agents. Their clinical usage is, however, limited by the lack of efficient methods for parenteral administration. Delivery via multi-functional nanoparticles is a potential solution to this problem. However, current nanoparticle manufacturing methods, which are based on bulk mixing of multiple reagents, have had only limited success in pre-clinical and clinical trials. Since bulk mixing is heterogeneous at local environment and consequently leads to the nanoparticles with poorly defined and non-uniform structures and compositions, we hypothesize that efficient and safe delivery can be achieved by tightly controlling the size, structure, and compositions of the synthetic nanoparticles. We therefore propose to employ microfluidic technology, which is capable of precisely controlling the mixing process at the micrometer scale, to the synthesis of multi-functional nanoparticles with uniform and well-defined structures and compositions for the delivery of therapeutic oligonucleotides to cancer cells. Our specific aims are (1) to optimize and validate microfluidic systems for the synthesis of multi-functional polymer and lipid-based nanoparticles containing synthetic miR (e.g., miR29b) and oligodeoxyribonucleotide (e.g., G3139) compounds targeting specific antiapoptotic proteins e.g., Bcl-2 and Mcl- 1, respectively, in melanoma and acute myeloid leukemia cells;and (2) to conduct in vitro and in vivo preclinical studies to characterize delivery efficiency, toxicity, biocompatibility, pharmacokinetics, biodistribution, and therapeutic efficacy of the microfluidic-based nanoparticles. If successful, this could lead to development of a new treatment modality for cancers such as melanoma and leukemia. Project Narrative: Oligonucleotides (especially micro RNA) hold great potential to become a new class of anticancer drugs, but their clinical applications are limited by a lack of efficient delivery methods. We seek to solve this problem by developing nanoscale, multi-functional, particle-like devices capable of delivering oligonucleotide drugs to cancer cells efficiently. The nanodevices will be assembled through a novel approach based on the precise manipulation of liquid flows at micrometer scale.